HP-IB Bus Structure

A b l e t o t a l k

DEVICE D

A b l e t o t a l k o n l y

pg635d

I

D A T A 8US ( 8 s i g n a l l i n e s )

, HANDSHAKE LINES

Figure 11-2. HP-IB Bus Structure

Data Bus

The data bus consists of 8 bidirectional lines that are used to transfer data from one device to another. Programming commands and data transmitted on these lines are typically encoded in ASCII, although binary encoding is often used to speed up the transfer of large arrays.

Both ASCII- and binary-data formats are available to the analyzer. In addition, every byte transferred over HP-IB undergoes a handshake to insure valid data.

HandshakeLines

A three-line handshake scheme coordinates the transfer of data between talkers and listeners. lb insure data integrity in multiple-listener transfers, this technique forces data transfers

to occur at the transfer rate of the slowest device connected to the interface. With most computing controllers and instruments, the handshake is performed automatically, making it transparent to the programmer.

Control Lines

The data bus also has five control lines The controller uses these lines to address devices and to send bus commands.

IFC (Interface Clear)

This line is used exclusively by the system controller. When

 

this line is true (low), all devices (whether addressed or not)

 

unaddress and revert to an idle state.

CompatiblePsripherals 11-17

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HP 8753E manual HP-IB Bus Structure, Unaddress and revert to an idle state